In order to guarantee the solidity of buildings' walls or of other concrete works, it is foreseen to have at its disposal an additional vertical framework inside the walls. A common technique consists in using this formwork system as a permanent or integrated formwork, that is to say, with a formwork which subsists as an integral part of the wall after having poured concrete on the inside.
The documents EP0883719 and WO02/38878 describe a formwork comprising an outer wall and a backing wall, these walls, called formwork walls, include vertical stiffeners made up of section bars, generally U-shaped. The formwork walls are linked by connection devices, each of them made up of a slightly zigzagging bent bar which is articulated at the level of the stiffeners. Between the formwork walls, these devices maintain a determined space into which the concrete is poured.
WO03/010397 describes the formwork of the above-mentioned documents where framework elements are introduced between the lateral sides of the U-shaped sections of two stiffeners placed opposite each other on each wall. Each framework element includes at least one vertical bar and at least two horizontal bars adjusted to slide into the stiffeners section. This framework element is added after opening out the formwork walls by sliding in the stiffeners, which act as guide rails. The U-shaped form of these stiffeners ensures the maintenance and the stability of this framework element and also facilitates its insertion.
The different elements of the formwork such as the formwork walls, the connection devices and the stiffeners are factory pre-fabricated, then assembled with the aid of appropriate fasteners to form the formwork. Formwork produced in this way leaves the factory in a folded form thanks to articulations of connections elements on the stiffeners, then it is opened out on the building site at the time of its installation to compose a wall.